The present invention relates to a device and method for alignment of the chassis of a wheeled vehicle. It has particular application in relation to the alignment of the chassis of go-karts and will be described in relation to that application. However, it should be understood that the invention may readily be adapted for use on many other wheeled vehicles.
The proper alignment of the chassis and the mounting of wheels thereto is an important element in the handling of any wheeled vehicle. A particularly important aspect of this chassis alignment is the alignment of the wheels which steer the vehicle which are usually the front wheels. While wheel alignment equipment for passenger vehicles such as conventional motor cars and commercial vehicles such as trucks are well known; they usually comprise very expensive installations which are permanently installed within a workshop. However the alignment of the steering wheels of a go-kart present factors which make such devices inapplicable. Go-karts are primarily used as competition vehicles where performance is the most important criteria. To obtain the ultimate performance from a particular go-kart, the set-up of the steering and chassis must be adjusted to suit each particular racetrack. Adjustments are required on race day and sometimes during the race itself. At the same time go-karts are intended as a relatively inexpensive form of motor racing such that the average competitor cannot afford very expensive equipment. Because of these reasons, methods for chassis alignment of go-karts have been limited to rather simple techniques and equipment. As the sport of go-kart racing has developed, the traditional methods have been found to be of insufficient accuracy for setting up a go-kart for racing.
Accordingly, the invention resides in a chassis alignment system comprising an alignment tool associated with a target, the alignment tool comprising a housing accommodating a laser emitting means, the housing having a mounting means adapted to enable the tool to be fixed to a first steerable axle and to be movable therewith, the laser emitting means being disposed in the housing at a predetermined distance from the mounting means, the mounting means being further adapted to enable the laser emitting means to be oriented about the central axis of the first steerable axle into a selected orientation, the laser beam being adapted to be emitted in a direction parallel to the central axis, the target comprising means to receive the first laser beam and provide an indication of the position at which the first laser beam is incident upon the target relative to a reference, the target adapted to be positioned relative to the vehicle to enable the orientation of the first steerable axle relative to an opposed, second steerable axle to be ascertained.
According to a preferred feature of the invention, the target is adapted to be fixed to the opposed, second steerable axle and to be movable therewith, the reference of the toe-in/camber target being spaced and oriented from the second steerable axle in a manner corresponding with the spacing and orientation of the laser emitting means from the first steerable axle.
According to a preferred feature of the invention, the target comprises indicia marked relative to a reference point.
According to a preferred embodiment, the mounting means comprises a clamp integral with the housing.
According to a preferred embodiment, the mounting means comprises an aperture integral with the housing, the aperture adapted to be received by the steerable axle to be secured thereto.
According to a preferred feature of the invention, the alignment tool further comprises an orienting means adapted to enable the alignment tool to be oriented to a datum. According to a preferred embodiment, the orienting means comprises a spirit level associated with the housing to provide a reference for orienting the housing.
According to a preferred feature of the invention, the target comprises a second alignment tool, the second tool being of the same type as the first alignment tool.
According to a preferred feature of the invention, the alignment tool further comprises a further laser emitting means, the further laser emitting means being adapted to emit a further laser beam in a direction substantially transverse to that of the first laser beam.
According to a preferred feature of the invention, the alignment tool is associated with a king-pin target adapted to intercept the beam from the further laser emitting device, the king-pin target comprising a reference point, an indication relative to a datum and a angular gauge indicating angular displacement from said indication about said reference point. According to a preferred embodiment, the reference point, indication and angular gauge are provided on a planar face. According to a preferred embodiment, the king-pin target is adapted to be mounted to a rear axle of the vehicle, the indication being parallel to the axis of said rear axle when mounted thereto.
According to a further aspect, the invention resides in a method of measuring the toe-in angle of the steering geometry of a vehicle, the method comprising the steps of mounting relative to each of steerable axles of the vehicle an alignment tool of the type as previously described, co-aligning the alignment tools relative to each other, and positioning the steering so that the horizontal position of each beam on the opposed respective target corresponds with the horizontal position of the opposed beam on its respective target.
According to a further aspect, the invention resides in a method of measuring the camber angle of the steering geometry of a vehicle, the method comprising the steps of mounting relative to each of steerable axles of the vehicle an alignment tool of the type as previously described, co-aligning the alignment tools relative to each other, and positioning the steering so that the vertical position of each beam on the opposed respective target corresponds with the vertical position of the opposed beam on its respective target.
According to a further aspect, a castor gauge is associated with a pair of alignment tools, the castor gauge being adapted to indicate the castor angle by use of the alignment tools. According to a preferred feature of the invention, the castor gauge comprises a reference point, an indication relative to a reference plane and a angular gauge indicating angular displacement from said indication about said reference point. According to a preferred embodiment, the castor gauge comprises a pair of parallel faces wherein the reference point is positioned on at least one face. According to a preferred embodiment, the material between the pair of parallel faces is substantially transparent or translucent.
According to a further aspect, there is disclosed a method of orienting the steering of a vehicle in a straight-ahead direction, the method comprising the steps of mounting relative to each of the steerable axles of the vehicle an alignment tool of the type as previously described, co-aligning the alignment tools relative to each other, positioning a target at an equal distance between each of the alignment tools, the target comprising a pair of parallel faces having a reference point referable to each face, and positioning the target so that the beam from each alignment tool is incident upon a respective face at the position referable to said reference point, each beam being incident upon the respective face substantially normal to that face.
According to a further aspect, the invention resides in a method of measuring the castor angle of the steering geometry of a vehicle, the method comprising the steps of mounting a pair of alignment tools as previously described relative to each of the steerable axles of the vehicle, co-aligning the alignment tools relative to each other, positioning the steering to a straight-ahead direction, positioning a castor gauge mid-way between the two alignment tools, the castor gauge comprising a reference point, an indication relative to a reference plane and a angular gauge indicating angular displacement from said indication about said reference point, orienting the castor gauge to align the indication parallel to a datum, and thereafter moving the steering to cause the beam from one alignment tool to be moved away from the reference towards the angular gauge to enable the angular displacement of the beam from the indication to be observed.
According to a preferred feature of the invention, the datum is adjusted to a horizontal reference and the orientation reference of the castor gauge is made relative to a horizontal reference plane. According to a preferred embodiment horizontal reference plane is ascertained by reference to a vertical reference.
According to a further aspect, the invention resides in a method of indicating the king-pin inclination angle of the steering geometry of a vehicle, the method comprising the steps of mounting an alignment tool as previously described relative to a respective steerable axle of the vehicle with the further beam directed rearwardly, positioning the steering to a straight-ahead direction, positioning a target to intercept the beam from the further laser emitting means, the target comprising a reference point, an indication relative to a datum and a angular gauge indicating angular displacement from said indication about said reference point aligning the target relative to the alignment tool so that the beam strikes a reference point on the target, and moving the steering to displace the beam to a position on the target such that the angular displacement of the further beam from the indication about the reference point provides an indication of the king-pin inclination angle.
According to a further aspect, the invention resides in a chassis alignment tool comprising a housing accommodating a laser emitting means, the housing having a mounting means adapted to enable the tool to be fixed to a first steerable axle of a vehicle and to be movable therewith, the first steerable axle having a central axis, the laser emitting means being disposed in the housing at a predetermined distance from the mounting means and adapted, in use, to emit a beam in a direction parallel to the central axis, the mounting means being further adapted to enable the laser emitting means to be oriented about the central axis into a selected orientation.
The invention will be more fully understood in the light of the following description of two specific embodiments.